As in so many other situations prevention is better than cure, and a kitchen or store should be built so that conditions are as unfavourable as possible for pests. During the actual construction of a building care should be taken to avoid leaving any cavities or cracks in which dust and scraps of food can accumulate and which are too inaccessible for proper cleaning. Such places may be ideal for certain pests. Bookcases and cupboards should either fit tightly to the floor or be free-standing with a clear space below them.
Cupboards and drawers should close properly and it is better to avoid panelling on walls and ceilings with cavities behind. In food factories the covers to machinery should be easily removable, so that frequent and thorough cleaning presents no problem. Foodstuffs must be kept as cool and dry as possible. In a store the goods should not be stacked right up against an external wall, but placed on low racks so that there is ventilation from all sides, and it is possible to sweep underneath them.
Cleanliness is important as dust and waste in cracks and crevices provide favourable breeding grounds for all sorts of pests.
In a kitchen or dining room it is best to store foodstuffs in tight-fitting containers, but there is no guarantee that they have not been infected beforehand. Many pests have an incredible ability to find their way into containers that seem sealed. Foodstuffs should not be kept longer than is absolutely necessary, especially if there has been a previous history of pest infestation in the kitchen. It may be better, at first, to buy food in smaller amounts and to keep those items most liable to attack in the refrigerator until one is quite sure that the pests have been eradicated. As already mentioned (p. 10) pests must come from somewhere and one way of preventing their spread is to go out and look for the source of infestation. In a factory such animals often arrive with raw materials. Suspicious looking parcels should therefore be examined and possibly treated before they come into the work area or at any rate kept separate from the finished goods for as long as possible. Returned goods and packing, empty sacks and containers with production waste are also a common source of infestations. Here again the same principle applies, and they should be kept well apart from raw materials, finished goods and packing material.
Sometimes pests are found in groceries in the house. If such animals are observed in newly purchased items it is in the interests of the grocer to tell him about this so that he can examine his store and isolate any infested goods. In a block of flats the animals may also come from other flats via ducts and piping.
Netting over windows and doors can be very effective in keeping occasional flying insects out of food factories or houses. In cases where the doors have to remain open owing to the volume of traffic it is possible to install a kind of air vent, the opening having a continuous stream of air through which the insects cannot fly.
It will always be easier to keep insects and mites out of food factories if a belt (about 2 metres broad) around the building is kept free of vegetation. If it should be necessary to spray or powder with poison in order to keep away undesirable intruders this can be done in such a belt, without adversely affecting the surrounding fauna.